Competitive Photoisomerization and Energy Transfer Processes in Fluorescent Multichromophoric Systems

Multichromophoric systems showing both fluorescence and photoisomerization are fascinating, with complex interchromophoric interactions. The experimental and theoretical study of a series of compounds, bearing a variable number of 4‐dicyanomethylene‐2‐tert‐butyl‐6‐(p‐(N‐(2‐azidoethyl)‐N‐methyl)aminostyryl)‐4H‐pyran (DCM) units are reported. The photophysical properties of multi‐DCM derivatives, namely 2DCM and 3DCM, were compared to the single model azido‐functionalized DCM, in the E and Z isomers. The (EE)‐2DCM and (EEE)‐3DCM were synthesized via the click reaction. Steady‐state spectroscopy and photokinetics experiments under UV or visible irradiation indicated the presence of intramolecular energy transfer processes among the DCM units. Homo‐ and hetero‐energy transfer processes between adjacent chromophores were confirmed by fluorescence anisotropy and decays. Molecular dynamics simulations for 2DCM were carried out and analyzed using a Markov state model, providing geometrical parameters (orientation and distance between chromophores) and energy transfer efficiency. This work contributes to a better understanding and rationalization of multiple energy transfer processes occuring within multichromophoric systems.